Why not go see your GP and get them on the NHS?
Your GP, will likely know your medical history, and could turn round and say, no the risk is to great, but if you the patient are willing to take the risk, then probably best go through a online website, and get your Viagra
I have low blood pressure and a slow heart, and I'm told I shouldn't take these tablets, as they may cause me problems, but in the time I have taken various tablets, and never had any problems
But each person must make up there own minds